The invention relates to a method for adapting a friction coefficient of an automated clutch, in which a current friction value is determined by comparison with a torque of the internal combustion engine during a slipping phase of the clutch.
In automated clutch applications, such as in duplex clutch and multiple clutch applications, the precise knowledge of the clutch torque is mandatory for good shifting and/or starting quality of a motor vehicle. Here the ability to predict the clutch coefficient is of great importance, because the control of the clutch occurs based on said clutch coefficient, since the typical shifting times and/or starting times of the clutch are below 1 second, which prevents any adaptation of the clutch coefficient in real time. The clutch coefficient is typically parameterized by a sensor point and the effective friction value and also adapted. The adaptation of the friction value occurs here by comparison with the torque of the internal combustion engine during the slipping phase of the active clutch.
A method is known from DE 10 2010 024 941 A1 for controlling a duplex clutch with two sub-drivetrains, allowing each of them to be coupled via a clutch to an internal combustion engine. During drive operation of the vehicle comprising the duplex clutch a sensor point of the clutch is determined, regardless of the motor torque. This sensor point is here determined during the start of operation of the vehicle, and then adapted during operation of said vehicle.
A method is known from DE 10 2013 204 831 A1 for determining parameters of a clutch in order to set the sensor point at which a pre-stress characteristic curve is determined.
The adaptation of the friction value can occur only when the clutch is monitored. Here, allowing monitoring means that the clutch is in a slipping operation and sufficient torque is transmitted thereby. In normal drive situations of the vehicle there are times during which the clutch cannot be monitored and thus the friction coefficient cannot be adapted. During these times the clutch is subject to changes due to cooling. Simultaneously, the clutch cannot be monitored when the vehicle is stationary, although the cooling of the clutch can lead to changes of the clutch characteristics.